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R. J. FLEMING.

MANUFACTURE OF BIFOCAL LENSES AND APPARATUS THEREFOR.

APPLICATION man JUNE 13. 9m. v 1

Patented May 27,1919;

I Improvements in the nonnnnqn a ss summer, or LONDON, ENGLAND.

nanurndrnnnior Lnnsns AND APPARATUS mansion Apiflicationfled June 13,

To all whom it may concern? a Be it known that 1, ROBERT J AMEs Film-- ING, asubject of the. King of Great Britain, 1 residing at. 136-142 Clerkenwell road, Lon-.

have invented new and useful don, England,

Manufacture of Bifocal Lenses and Apparatus Therefor, of which the following is a specification.

My invention relates to a method of and apparatus for "the manufacture of bifocal lenses.

is ground upon a lenslo'y curved grinding disk, which is preferably According to the invention the, lower field means of a flat or circular in shape and is caused to sweep around in a clrcular path and at the same I time to rotate upon its'ow-n axis by means of a'loose eccentric connection with a rotatingv eccentric pin 6 1s deslgned loosely ito e'nga e.

'' spindle. I

' In a sultable arrangement for carrying out the'invention Iprovide, aspindle having. an eccentric pm upon 1ts:lower-end,:the said eccentric pin engagmg in a central hole or depression in the grindingdisk. The rotation-'ofthe spindle not only canses thegrind ing disk to move in a circular path around the axis of the spindle but also causes it torotate upon the eccentric pin as a center, the

result. being that the whole .016 the field 1st frame a,.andtl1e other end at 1; tea sleevem ground and smoothed and polished in a most loosely mounted intlieflspindjldbf betWeeuLhe j' eii'ective manner.

In some cases the movement above described maybe comblned with'a lateral or .reciprocating or swinging or oscillating movement of the lens'beingground so as to produce an oval field. Also desired, the lower field may first be roughly. means of aciroular grindin tool; the'said field being subsequently finished and polished by the method above described.

' '.It,will be understood that suitable means are provided for applying thelgr'inding' disk to the glass with the necessary pressure andthat the inventlon is {applicable to the" pro;

ing spindle,

In the accompanying duction of bifocal lensesoffplaneor toric form.

an. f a machine for Figure 1 is a front'view o Fig. 21s a side view thereof.

' Fig. 3 is a sectional elevf ion disk and'lensj'beingground; Fig. 4 is a horizontal section on the line is a view similar tov Fig. 3, but

ground by action ofthe spiral spring 0,

of the spindle'b isf t around the axis of the- 1914. ser ia1no.s44,-sss.

' ing tool gated-lower field, and

Fig. 7 is'a'side view of apart of Pa ama 1919.,

Fig. 6 is a front view of a modified form. of machine'for producing an oval or eI0n-- Figs. 3 to 5 are drawn to a larger-scale than Figs. 1, 2, 6, and 7. a 1

a represents the frame or standard of the machine, and b is the spindle which is mount-1 ed in the bearings '0, 00f the "framea, in

which bearings it is designed to be rotated by means of the pulleyd; 'from anysuitable source of power, not illustrated.v

lower endof the spindle b -and.;f is the grinde is the eccentric pln wh ch 11s fitted at the g with which the lower pointed en .of the.

h is the 'tab1e upon whichthelens A to' e ground is secured by cement or pitch, in -the it may. be adjusted.

Y Z is a T- haped lever one end of nifto'ri. zontal bar of which is pivoted "at .m' was;

'pulley d and hezcollarf-b secuf-ed tqfli i dle b. .The lower. end of the said T- shaped lever is connected to oneYbndOf a; spiral; sprlng 0, the other end of which is"attached to an adjusting screw ;The function of th s spring is, as will beobvious"; to ijaus'e the grinding-tool f to be applied to the surfaces 'of'the glassA' with therequisitepresfsure through the, medium of? the fr -sliapf;

The ap aratus operates follows: that 1s assuming that thelensA to he gr and he srindiugw a e f w c a is cemented to the table h and that the i s-d a curvature "which corresponds". to. that vto enter thejc'entralhole disk -f and topress the latter, under the for bvhand' produced upon thejlower field. of thelen's; is 1 placed in positionthereon the l'evenl isre. 'le'asedso as to permit theeccentric "pin 'e'to gin the said griiiding. I

pressura withfthe fequis'iteforce-against' the surfac'eof lens ,A to be ground. e

disk 7 to describe a-circle en set inrotationj, thus causing 110.

also simultaneously; to rotate around the o I of a bifocalfl'ens comprismg'ra rota-table eccentric pin 9 as a center, as shown in Fig. l. the result being that the field is ground to the curvature desired and of a circular shape.

As statedthe circular lower field may, if desired, be first roughly ground. for which "purpose the circular grinding tool (1. Fig.

is made use of, the field so ground being subsequentlv finlshed'and polished by means of the eccentricdisk f above described.

Figs 6 and 7 illustrate a modified con struct-ion of machine which is designed, to produce an elongated or oval lower field for which purpose a lateral or oscillatingmotion is given to the lens A. The shank i of the lens table h is adjust-ably mounted at its lower end in a socket 9 which is mounted on ,lateral pivots or trunnions s in a sleeve 25,

' adjustablv carriedupon a fixed r'od u of of an elongated nature.

the frame. The table shank 2' works in a guide 2' on the f nine (1 and its upper end is proi'ided with a vertical slot c" with which engages a. crank pin wupon a crank disk :0

carried by a spindleymounted in a bearing in the f 'ame aand designed to be rotated by thepulley z; i As will be ob'viou'sthis form of the machine operates asfollows, that is to say, as-

suming'that the lens A, be in position and thecmachine started, the grinding disk f is caused to rotate on its own axis and to swing inf'a' circle around the spindle Z) as above described and at the same time an oscillating motion" is imparted to the lens A by the crank pin w so'that the actual shape of the field which is produced upon the lens A is It will be under stood that the distance between the surface of the'd'ens being ground and the pivot-s must be adjusted so that itequals the radius of curvature to be given to the field. It will also be understood that the surface ground 'wi'll'be convex".v ll liere a concave lower field is required the'lens holder is arranged to have a correspondinginotionimparted to it, ior. whiclrpurpose' 1t may, for example, be

suspendedfrom' a "pivot' situated at the proper distance above-the lens.

Clannsz" I 1. A machine for grinding the lower field spindle, a" pinmounted 'eocentrically upon ,said spindle, and adens-holding member;

havingla teral movement at right-angles to the axis of the rotatable spindle. 2-. In a machine for grindin field of a bifocal lens, the combination of a rotatable spindle, an eccentric pin projecting from said spindle, a table mounted for movethe lower I ment transversely with respect to the axis oft-the spindle, a grinding member, a lens-- holding member, one of the last-nainel 1nembers being provided. with a depression in which the end of the said eccentiic pin loosel; bears, the other one oi the last-named members being connected fixedly with the table, and means for operating the spindle- -and table simultaneously.

3. I11 a machlne for grinding the. lower held of a bifocal lens, the combination of a rotatable spindle, an eccentric pin pro1ect- .lng from said spindle, an oscillating table mounted with its pivotal axis nitersecting the axis ofthe spindle, a grinding member,

a lens-holding member, one of the last-minted members being pronded witlra depress on in which the end of the said eccentric pin loosely bears, the other one of the last-named members being connected fixedly with the. table. and means for operating the spindle and the table simultaneously.

l. A machine for grinding the lower field of a bifocal lens including a rotatable spin- I dle,- an eccentric pin projecting from said spindle, an oscillating table mounted with -its pivotal axis intersecting the axis of the spindle, a guiding means for the table, a crank element connected with the. table for oscillating the same, a grinding meml'ier a lens holding member, one of the last nan'ied members being provided with a depression in which the end of the eccentric pin loosely bears and the other one of the last :inentioned members being connected. fixedly with the table, and means for operating the spindle simultaneously with the table.

5. A machine for grinding the lower field of bifocal lens including a frame, a guide carried bythe frame and having a depending vertical rod, a sleeve adjustably mounted on the rod, 3. socket pivotally connected with the sleeve and carried by the same, an oscillating' table having a shank operating in the 

